When a user signs up, Zotonic verifies the validity of some
information, such as the e-mail address and the password strength. If
these verifications succeed, it stores the user data in the Zotonic
database. If you have your own database with project-specific user
data, you may want to insert additional information into this database
on sign up. To do this, you need to modify the sitename.erl file,
where sitename is the name of your site. Remember that this file is
located in user/sites/sitename/.